My broad goal is to elucidate mechanisms by which neurons form specific synapses at precisely targeted locations. One major determinant of synaptic specificity is laminar specificity, the restriction of particular axonal arbors to specific laminae within the target area. The widespread and prominent presence of laminar specificity throughout the central nervous system is indicative of its fundamental importance. Recent work from the Sanes laboratory provided clues that one such family of molecules, Sidekicks (Sdks), mediate this developmental process in the retina. Using the mouse retina as a model system, I will use cellular and genetic approaches to functionally test the role of Sdks. I hypothesize that Sidekicks are determinants of lamina- specific synaptogenesis.